What does Exodus 7:23 mean?

Pharaoh further proves himself to be a stereotypical tyrant. He oversees brutal slavery (Exodus 1:11–14). He ignores and mocks requests for freedom (Exodus 5:1–5). He retaliates against those who even speak about it (Exodus 5:6–9). He ignores evidence he does not like (Exodus 7:10–13). Here, he appears callous about the damage being done to his people. When the Nile turns into blood (Exodus 7:20–21), his only recorded response is indifference: he goes home. The Hebrew phrase used here contains the same word found when referring to his hardened "heart." This expression could be paraphrased to mean, "it did not affect him," or "he didn't care."

The plagues in Egypt (Exodus 3:19–20) will escalate as they continue. Yet, each time, Pharaoh will find enough stubbornness to refuse to let Israel go (Exodus 5:1–3). Only when the results are intimately personal—the death of his own son (Exodus 4:21–23; 12:29–32)—will he submit. Even then, his pride will only allow this for a short time (Exodus 14:5–7).